U.S. patent application number 16/686290 was filed with the patent office on 2020-03-19 for super-absorbent swellable hot melt coated optical fibers, buffer tubes, cable designs thereof and manufacturing processes.
The applicant listed for this patent is CORNING RESEARCH & DEVELOPMENT CORPORATION. Invention is credited to Dana Craig Bookbinder, Ruchi Tandon.
Application Number | 20200088967 16/686290 |
Document ID | / |
Family ID | 64455603 |
Filed Date | 2020-03-19 |
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United States Patent
Application |
20200088967 |
Kind Code |
A1 |
Bookbinder; Dana Craig ; et
al. |
March 19, 2020 |
SUPER-ABSORBENT SWELLABLE HOT MELT COATED OPTICAL FIBERS, BUFFER
TUBES, CABLE DESIGNS THEREOF AND MANUFACTURING PROCESSES
Abstract
Embodiments of an optical fiber cable are provided. The cable
includes a cable jacket and at least one buffer tube. Each buffer
tube surrounds a plurality of optical fibers. The cable jacket
surrounds the at least one buffer tube. Further, a coating of
superabsorbent, swellable hot melt is applied to at least one of
the following locations: (i) along at least a portion of the length
of at least one of the plurality of optical fibers; (ii) along at
least a portion of the length of the exterior or interior surface
of the at least one buffer tube; or (iii) along at least a portion
of the length of the interior surface of the cable jacket.
Moreover, the superabsorbent, swellable hot melt is capable of
absorbing at least 50 g of water per gram of superabsorbent,
swellable hot melt.
Inventors: |
Bookbinder; Dana Craig;
(Corning, NY) ; Tandon; Ruchi; (Painted Post,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING RESEARCH & DEVELOPMENT CORPORATION |
Corning |
NY |
US |
|
|
Family ID: |
64455603 |
Appl. No.: |
16/686290 |
Filed: |
November 18, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US18/34686 |
May 25, 2018 |
|
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16686290 |
|
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62513033 |
May 31, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/4494 20130101;
G02B 6/441 20130101; G02B 6/4434 20130101; G02B 6/4433
20130101 |
International
Class: |
G02B 6/44 20060101
G02B006/44 |
Claims
1. An optical fiber cable comprising: a cable jacket having an
exterior surface and an interior surface; at least one buffer tube,
wherein each of the at least one buffer tube has an exterior
surface and an interior surface, wherein each of the at least one
buffer tube surrounds a plurality of optical fibers, and wherein
the cable jacket surrounds the at least one buffer tube; wherein a
coating of superabsorbent, swellable hot melt is applied to at
least one of the following locations: (i) along at least a portion
of the length of at least one of the plurality of optical fibers;
(ii) along at least a portion of the length of the exterior or
interior surface of the at least one buffer tube; or (iii) along at
least a portion of the length of the interior surface of the cable
jacket; and wherein the superabsorbent, swellable hot melt is
capable of absorbing at least 50 g of water per gram of
superabsorbent, swellable hot melt.
2. The optical fiber cable of claim 1, wherein the coating is
applied to location (i) or location (ii) and wherein the coating of
superabsorbent, swellable hot melt has alternating sections of the
coating separated from each other by uncoated portions along the
length of the optical fiber or of the buffer tube.
3. The optical fiber cable of claim 1, wherein the sections of
coating and the uncoated portions each have a length of between 1
mm and 100 mm.
4. The optical fiber cable of claim 1, wherein the coating is
applied to location (i) or location (ii) and wherein the coating of
superabsorbent, swellable hot melt extends around less than the
entire circumference of the optical fiber or of the buffer
tube.
5. The optical fiber cable of claim 4, wherein the coating covers
between 5% and 50% of the circumference of the optical fiber.
6. The optical fiber cable of claim 1, wherein the plurality of
optical fibers is N optical fibers; wherein each buffer tube has an
outside diameter D1; wherein each optical fiber has an outside
diameter D2 such that D2 is less than 210 microns and greater than
100 microns; and wherein the N optical fibers are densely packed
within each buffer tube such that a diameter ratio parameter,
.OMEGA., is defined as the ratio D1/D2, and is
2.25+0.143(N).ltoreq..OMEGA..ltoreq.1.14+0.313(N).
7. The optical fiber cable of claim 1, wherein the coating of
superabsorbent, swellable hot melt has a thickness t.sub.hm that is
1 micron.ltoreq.t.sub.hm.ltoreq.200 microns.
8. The optical fiber cable of claim 1, wherein the coating of
superabsorbent swellable hot melt comprises superabsorbent polymer
powder particles having an average diameter of >1 micron and
<100 microns.
9. The optical fiber cable of claim 8, wherein less than 50% of the
superabsorbent polymer powder particles have a maximum outer
dimension .gtoreq.50 microns.
10. The optical fiber cable of claim 8, wherein less than 10% of
the superabsorbent polymer powder particles have a maximum outer
dimension .gtoreq.38 microns.
11. The optical fiber cable of claim 1, wherein the cable further
includes at least one flame retardant additive.
12. The optical fiber cable of claim 11, wherein the at least one
flame retardant additive comprises at least one of aluminum
trihydrate, magnesium hydroxide, smoke suppressant molybdenum-based
particles, ammonium polyphosphate, or pentaerythritol.
13. The optical fiber cable of claim 1, wherein the coating of
superabsorbent, swellable hot melt comprises at least one of sodium
or potassium sodium acrylate or acrylamide copolymers, cross-linked
carboxymethylcellulose, ethylene maleic anhydride copolymers,
cross-linked polyethylene oxide, polyvinyl alcohol copolymers, or
starch-grafted copolymers of polyacrylonitrile.
14. The optical fiber cable of claim 1, wherein the plurality of
optical fibers are one of loose optical fibers or optical fibers
bound by a ribbon matrix.
15. The optical fiber cable of claim 1, wherein each of the
plurality of optical fibers comprises a glass core, a cladding, and
a layer of non-superabsorbent polymer that surrounds the cladding;
wherein the coating is applied to the at least one of the plurality
of optical fibers; and wherein an inner surface of the coating of
the superabsorbent, swellable hot melt contacts an outer surface of
the layer of non-superabsorbent polymer.
16. A method of fabricating an optical fiber cable comprising the
steps of: applying a coating of superabsorbent, swellable hot melt
along at least a portion of a length of an optical fiber; and
arranging within a buffer tube a plurality of optical fibers in
which at least one of the plurality of optical fibers is an optical
fiber having the coating such that a gap between any two adjacent
optical fibers is less than a diameter of any one of the plurality
of optical fibers.
17. The method of claim 16, further comprising the step of
including in the superabsorbent, swellable hot melt at least one of
sodium or potassium sodium acrylate or acrylamide copolymers,
cross-linked carboxymethyl cellulose, ethylene maleic anhydride
copolymers, cross-linked polyethylene oxide, polyvinyl alcohol
copolymers, or starch grafted copolymers of polyacrylonitrile.
18. The method of claim 17, wherein the step of applying the
coating of superabsorbent, swellable hot melt further comprises
applying the coating over 5% to 50% of the circumference of the
optical fiber.
19. The method of claim 17, further comprising the step of mixing
the superabsorbent, swellable hot melt with at least one of
aluminum trihydrate, magnesium hydroxide, smoke suppressant
molybdenum-based particles, or ammonium polyphosphate,
pentaerythritol.
20. An optical fiber cable, comprising: a cable jacket having an
exterior surface and an interior surface; at least one buffer tube,
wherein each of the at least one buffer tube has an exterior
surface and an interior surface and wherein the at least one buffer
tube is surrounded by the outer cable jacket; a plurality of
optical fiber ribbons arranged in a stack within each of the at
least one buffer tube, each of the optical fiber ribbons comprising
a plurality of optical fibers surrounded by and supported within a
polymeric ribbon matrix; wherein a coating of superabsorbent,
swellable hot melt is applied to at least one of the following
locations: (i) along at least a portion of the length of at least
one of the plurality of optical fiber ribbons; (ii) along at least
a portion of the length of the exterior or interior surface of the
at least one buffer tube; or (iii) along at least a portion of the
length of the interior surface of the cable jacket; and wherein the
superabsorbent, swellable hot melt is capable of absorbing at least
50 g of water per gram of superabsorbent, swellable hot melt.
Description
PRIORITY APPLICATIONS
[0001] This application is a continuation of International
Application No. PCT/US18/34686, filed on May 25, 2018, which claims
the benefit of priority to U.S. Application No. 62/513,033, filed
on May 31, 2017, both applications being incorporated herein by
reference.
BACKGROUND
[0002] The disclosure relates generally to cables and more
particularly to optical fiber cables having a coating of
superabsorbent, swellable hot melt on at least one of the interior
of a cable jacket, the interior or exterior of a buffer tube, or
along the length of an optical fiber. Optical cables have seen
increased use in a wide variety of field's including various
electronics and telecommunications fields. Optical cables contain
or surround one or more optical fibers. The cable provides
structure and protection for the optical fibers within the
cable.
SUMMARY
[0003] In one aspect, embodiments of an optical fiber cable are
provided. The optical fiber cable includes a cable jacket having an
exterior surface and an interior surface and at least one buffer
tube. Each of the at least one buffer tube has an exterior surface
and an interior surface, and each of the at least one buffer tube
surrounds a plurality of optical fibers. The cable jacket surrounds
the at least one buffer tube. Further, a coating of superabsorbent,
swellable hot melt is applied to at least one of the following
locations: (i) along at least a portion of the length of at least
one of the plurality of optical fibers; (ii) along at least a
portion of the length of the exterior or interior surface of the at
least one buffer tube; or (iii) along at least a portion of the
length of the interior surface of the cable jacket. Moreover, the
superabsorbent, swellable hot melt is capable of absorbing at least
50 g of water per gram of superabsorbent, swellable hot melt.
[0004] In another aspect, embodiments of a method of fabricating an
optical fiber cable are provided. The method includes the steps of
applying a coating of superabsorbent, swellable hot melt along at
least a portion of a length of an optical fiber and arranging
within a buffer tube a plurality of optical fibers. At least one of
the plurality of optical fibers is an optical fiber having the
coating. Further, the optical fibers are arranged such that a gap
between any two adjacent optical fibers is less than a diameter of
any one of the plurality of optical fibers.
[0005] In still another aspect, embodiments of another optical
fiber cable are provided. The optical fiber cable includes a cable
jacket having an exterior surface and an interior surface and at
least one buffer tube. Each of the at least one buffer tube has an
exterior surface and an interior surface, and the at least one
buffer tube is surrounded by the outer cable jacket. The optical
fiber cable also includes a plurality of optical fiber ribbons
arranged in a stack within each of the at least one buffer tube.
Each of the optical fiber ribbons includes a plurality of optical
fibers surrounded by and supported within a polymeric ribbon
matrix. Further, a coating of superabsorbent, swellable hot melt is
applied to at least one of the following locations: (i) along at
least a portion of the length of at least one of the plurality of
optical fiber ribbons; (ii) along at least a portion of the length
of the exterior or interior surface of the at least one buffer
tube; or (iii) along at least a portion of the length of the
interior surface of the cable jacket. The superabsorbent, swellable
hot melt is capable of absorbing at least 50 g of water per gram of
superabsorbent, swellable hot melt.
[0006] Additional features and advantages will be set forth in the
detailed description that follows, and in part will be readily
apparent to those skilled in the art from the description or
recognized by practicing the embodiments as described in the
written description and claims hereof, as well as the appended
drawings.
[0007] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary, and are intended to provide an overview or framework to
understand the nature and character of the claims.
[0008] The accompanying drawings are included to provide a further
understanding and are incorporated in and constitute a part of this
specification. The drawings illustrate one or more embodiment(s),
and together with the description serve to explain principles and
the operation of the various embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings incorporated in and forming a part
of the specification illustrate several aspects of the present
invention and, together with the description, serve to explain the
principles of the invention. In the drawings:
[0010] FIG. 1 is a cross-sectional view of an optical fiber cable
usable with the superabsorbent, swellable hot melt (SA-SHM),
according to an exemplary embodiment;
[0011] FIG. 2 is a cross-sectional view of a buffer tube having a
lining of SA-SHM and containing optical fibers also having a
coating of SA-SHM, according to an exemplary embodiment;
[0012] FIG. 3A is a partial isometric view of an optical fiber with
a coating of SA-SHM that is discontinuous along its length,
according to an exemplary embodiment;
[0013] FIG. 3B is a cross-sectional view of an optical fiber with a
coating of SA-SHM that is discontinuous around its circumference,
according to an exemplary embodiment;
[0014] FIG. 4 is a cross-sectional view of an optical fiber cable
with the optical fibers arranged in ribbons, each ribbon having a
coating of SA-SHM, according to an exemplary embodiment; and
[0015] FIG. 5 is a graph representing the water swelling capacity
of three SA-SHM as a function of time, according to an exemplary
embodiment.
[0016] While the invention will be described in connection with
certain preferred embodiments, there is no intent to limit it to
those embodiments. On the contrary, the intent is to cover all
alternatives, modifications and equivalents as included within the
spirit and scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION
[0017] Referring generally to the figures, various embodiments of
an optical fiber cable having one or more cable component coated
with superabsorbent, swellable hot melt (SA-SHM) are shown. In
embodiments, the use of SA-SHM helps to alleviate issues with bend
losses experienced by optical fiber cables in their various
deployments, particularly those that utilize superabsorbent polymer
particles. In particular, the SA-SHM is used as a coating on the
inside of a optical fiber cable jacket, as a coating on or inside
buffer tubes, as a coating along at least a portion of the length
of at least one optical fiber, and/or as a coating on a least a
portion of the length of at least one ribbon of an optical fiber
cable. Furthermore, cables using the SA-SHM do not require
superabsorbent polymer (SAP) powders, SAP tapes, and/or SAP yarns,
which are a source of bend loss.
[0018] As shown in FIG. 1, an optical cable, shown as cable 10, is
illustrated according to an exemplary embodiment. Cable 10 includes
an outer cable jacket, shown as outer jacket 12, having an inner
surface 14 that defines an inner passage or cavity, shown as
central bore 16, and an outer surface 18 that generally defines the
outermost surface of cable 10. As will be generally understood,
inner surface 14 of jacket 12 defines an internal area or region
within which the various cable components discussed herein are
located.
[0019] In various embodiments, cable jacket 12 is formed from an
extruded thermoplastic material, which is not a superabsorbent
polymer material. In various embodiments, cable jacket 12 may be a
variety of materials used in cable manufacturing such as
polyethylene, medium density polyethylene, polyvinyl chloride
(PVC), polyvinylidene difluoride (PVDF), nylon, polyester or
polycarbonate and their copolymers. In addition, the material of
cable jacket 12 may include small quantities of other materials or
fillers that provide different properties to the material of cable
jacket 12. For example, the material of cable jacket 12 may include
materials that provide for coloring, UV/light blocking (e.g.,
carbon black), burn resistance, etc.
[0020] Cable 10 includes one or more optical transmission elements
or optical waveguides, shown as optical fibers 20. In the
embodiment shown, groups of optical fibers 20 are located in
separate buffer tubes 22, and buffer tubes 22 are wrapped (e.g., in
an SZ stranding pattern) around a central strength member 24. In
various embodiments, cable 10 includes at least four buffer tubes
22. Central strength member 24 may be any suitable axial strength
member, such as a glass-reinforced plastic rod, steel rod/wire,
etc. Generally, cable 10 provides structure and protection to
optical fibers 20 during and after installation (e.g., protection
during handling, protection from elements, protection from the
environment, protection from vermin, etc.).
[0021] In various embodiments, cable 10 also includes an armor
layer, shown as armor 26. In general, armor 26 is formed from a
strip of metal material (e.g., a metal tape, a flat elongate
continuous piece of material, etc.) that is wrapped around and
circumferentially surrounds buffer tubes 22. As shown in FIG. 1,
armor 26 is located adjacent to the inner surface 14 of outer
jacket 12 such that these two layers are in contact with each
other. In specific embodiments, armor 26 is corrugated steel tape
material that is wrapped around the interior portions of cable 10,
and in some of these embodiments, armor 26 is longitudinally folded
forming a longitudinal overlapped section where opposing edges of
the tape overlap to completely surround inner buffer tubes 22 (and
any other interior component of cable 10). In other embodiments,
armor 26 may be a strip of metal tape material, helically wrapped
around buffer tubes 22 such that armor 26 forms a layer
circumferentially surrounding buffer tubes 22. In general, armor
layer 26 provides an additional layer of protection to fibers 20
within cable 10, and may provide resistance against damage (e.g.,
damage caused by contact or compression during installation, damage
from the elements, damage from rodents, etc.). Cable 10 may include
a variety of other components or layers, such as helically wrapped
binders, circumferential constrictive thin-film binders, etc.
[0022] In the embodiment shown, cable 10 includes one or more
preferential tear feature and/or ripcord 28 embedded in or
underneath jacket 12. In this embodiment, the preferential tear
feature and/or ripcord 28 is located within jacket 12 such that
ripcord 28 facilitates opening of outer jacket 12. In some
embodiments, ripcord 28 may be located within armor layer 26 such
that ripcord 28 facilitates opening of both armor 26 and jacket
12.
[0023] In embodiments, cable 10, optical fibers 20 and buffer tube
22 are configured in various ways to provide a high fiber density
and high fiber count cable while at the same time reducing or
minimizing buffer tube size and/or cable jacket size. As discussed
herein, low diameter optical fiber allows higher density and
smaller cable, and the low bend loss design of these optical fibers
allows such high density, small cables to have acceptable signal
loss properties.
[0024] In addition, bend losses may be greater in cables in which
optical fibers are densely packed in relatively rigid buffer tubes,
are densely packed within a cable jacket and/or are densely packed
in an optical fiber ribbon arrangement. Bend losses in such cables
are caused, at least in part, by positional constraint resulting
from the dense packing which limits the ability of optical fibers
to shift to assume low strain positions during bending,
compression, etc. For example, in certain optical fiber cables
using SAP powder as a means to absorb water, the SAP powder
particles can, in some circumstances, cause microbending of the
optical fibers 20 particularly when the optical fibers 20 are
densely packed, which can result in undesirable attenuation. That
is, in some optical fiber cables, the geometry (generally,
shard-like) and size (>100 microns) of the SAP powder particles
can, in some circumstances, cause microbending in densely packed
optic fibers and prevent the optical fibers from assuming low
strain positions. Thus, typical optical fiber cable and/or buffer
tube configurations include a significant amount of free-space
between the outer surfaces of the optical fibers and the inner
surface of the buffer tube or jacket, and this free-space allows
the optical fibers to move or shift to assume low strain positions
during bending. By reducing strain that the optical fibers
experience during bending, such low density cables provide a
satisfactory level of signal attenuation, but do so with a
relatively large diameter buffer tube and/or relatively large cable
jacket.
[0025] By comparison, in the embodiment depicted in FIG. 2, the
buffer tube 22 surrounds densely packed optical fibers 20. In an
embodiment, a diameter ratio parameter .OMEGA. is defined between
the inner diameter D1 of the buffer 22 and an outer diameter D2 of
each of N number of optical fibers 20 (i.e., .OMEGA.=D1/D2). In a
specific embodiment, the diameter ratio parameter .OMEGA. is
selected such that
2.25+0.143(N).ltoreq..OMEGA..ltoreq.1.14+0.313(N). In embodiments,
the number N of optical fibers 20 is at least four. In specific
embodiments, the number N of optical fibers 20 is 12, the inner
diameter D1 of the buffer tube is 15 mm, and the outer diameter D2
of each optical fiber 20 is less than 210 microns and greater than
100 microns. In another embodiment in which the number N of optical
fibers 20 is greater than 6, the diameter ratio parameter .OMEGA.
is selected such that .OMEGA..ltoreq.2.66+0.134(N).
[0026] In still other embodiments, the optical fibers 20 are
arranged in such a way that a gap G between adjacent optical fibers
20 is smaller than the diameter D2 of any individual optical fiber
20. Additionally, the gap between any optical fiber 20 and the
interior surface of the buffer tube 22 is smaller than the diameter
D2 of any individual optical fiber 20. That is, the optical fibers
20 are arranged within the buffer tube 22 in such a way that no
space large enough to accommodate an additional optical fiber 20 is
provided within the buffer tube 22.
[0027] The packing of the optical fibers 20 within the buffer tube
in the previously described manners is facilitated by an SA-SHM
coating 30 that is applied at least partially around and at least
partially along the length of at least one of the optical fibers
20. Thus, while all of the optical fibers 20 of the embodiment
depicted in FIG. 2 are depicted with the SA-SHM coating 30,
embodiments exist where only one, two, three, etc. optical fibers
20 have the SA-SHM coating 30, and the remaining optical fibers 20
remain uncoated. In such embodiments, the SA-SHM coating 30 on only
some of the optical fibers 20 is enough to provide water protection
for all the optical fibers 20 within the buffer tube 22.
Advantageously, the SA-SHM coating 30 does not contribute to
microbending losses in the same manner as SAP powders, water
blocking tapes or SAP tapes, and/or SAP yarns, which means that the
optical fibers 20 can be placed closer together within the buffer
tube 22 without the concern of providing a substantial amount of
space for the optical fiber communication elements to move into low
strain positions.
[0028] In other embodiments, the SA-SHM coating 30 is located on
the interior surface of the buffer tube 22. In such an embodiment,
the SA-SHM coating 30 can be applied to a bundle of optical fibers
20, such as by spraying, atomizing, dip-coating, extruding,
fiberizing, etc. the SA-SHM coating 30 on the bundle of fibers 20
or by co-extruding the SA-SHM coating 30 with the buffer tube 22.
In another embodiment, the SA-SHM coating 30 is located on the
exterior surface of the buffer tube 22. In such an embodiment, the
SA-SHM 30 can be applied to the exterior surface of the buffer tube
22 by spraying, atomizing, dip-coating, extruding, fiberizing, etc.
or by co-extruding the SA-SHM coating 30 with the buffer tube 22.
In still another embodiment, the SA-SHM coating 30 is applied to
the interior surface 14 of the cable jacket 12, such as between the
cable jacket 12 and the armor 26 (if included). In such an
embodiment, the SA-SHM coating 30 can be applied to a bundle of
buffer tubes 22, such as by spraying, atomizing, dip-coating,
extruding, fiberizing, etc. the SA-SHM coating on the bundle of
buffer tubes 22 or by co-extruding the SA-SHM coating 30 with the
cable jacket 12.
[0029] Regardless of location, the SA-SHM coating 30 can have a
thickness ti of up to 200 microns in some embodiments. In other
embodiment, the SA-SHM coating 30 has a thickness of up to 50
microns, and in still other embodiments, the SA-SHM coating 30 has
a thickness of up to 30 microns. The SA-SHM coating also has a
thickness of at least 1 micron in embodiments.
[0030] The SA-SHM coating 30 can have various compositions.
However, generally, the water absorption capacities of the SA-SHM
coatings used in the embodiments of the optical fiber cables
disclosed herein will be greater than 50 grams of water absorbed
per gram of SHM coating. In other embodiments, the water absorption
capacity of the SHM coating is greater than 100 gram of water
absorbed per gram of SHM coating. In still other embodiments, the
water absorption capacity of the SHM coating is greater than 150
grams of water absorbed per gram of SHM coating. In yet other
embodiments, the water absorption capacity of the SHM coating is
greater than 200 grams of water absorbed per gram of SHM
coating.
[0031] In embodiments, the SA-SHM coating is comprised of a hot
melt matrix in which one or more superabsorbent polymer powders are
suspended. That is, the superabsorbent polymer powders are
distributed throughout the thickness of the hot melt matrix and not
just on a surface of the hot melt or not just to a certain depth of
the hot melt. The hot melt matrix additionally provides a
connective matrix by which to keep the coating together when the
superabsorbent polymer powders expand upon contacting water.
[0032] In some embodiments, the SA-SHM coatings used are physically
setting thermoplastic materials. For example, these may include
commercially available water-swellable hot melt adhesives such as
HM002 and HM008B (available from Stewart Superabsorbents, Hickory,
N.C.), Technomelt AS 4415 (also known as Macromelt Q 4415 available
from Henkel Corp., Madison Heights, Mich.), and NW1117 and NW1120B
(Hydrolock.RTM. super absorbent thermoplastic available from H. B.
Fuller Company, Vadnais Heights, Minn.).
[0033] Additionally, a variety of exemplary compositions are
provided in the following paragraphs. According to one embodiment,
the SA-SHM coating includes essentially three components that are
mixed homogenously. The first component is a water-insoluble
component containing at least one water-insoluble polymer or
copolymer and at least one other substantially water-insoluble
resin. For example, the first component can be selected from
polyamides, copolyamides, polyaminoamides, polyesters,
polyacrylates, polymethacrylates, polyolefins and ethylene/vinyl
acetate (EVA) copolymers. Further the first component can be
mixtures of one or more of the foregoing polymers. The second
component is a water-soluble or water-dispersible component
containing at least one water-soluble or water-dispersible oligomer
and/or polymer or copolymer. For example, the second component can
be selected from polyethylene glycols with molecular weights of 400
to 20,000, polyvinyl methyl ether, polyvinyl pyrrolidone,
copolymers of vinyl methyl ether or vinyl pyrrolidone, polyvinyl
alcohols, water-soluble or water-dispersible polyesters or
copolyesters, and water-soluble or water-dispersible acrylate
polymers.
[0034] The third component is a water-swellable component (i.e., a
superabsorbent polymer) consisting of a water-swellable homopolymer
or copolymer. For example, the third component can be selected from
any homopolymers and/or copolymers which, as hydrophilic materials,
are capable of absorbing and retaining large amounts of water, even
under pressure, without immediately dissolving in the water,
including, for example, graft copolymers of starch or cellulose
with acrylonitrile, acrylic acid or acrylamide, carboxymethyl
cellulose, maleic anhydride/poly-.alpha.-olefin copolymers,
polyacrylamide, polyacrylic acid and salts of polyacrylic acid,
and, optionally, copolymers of acrylic acid or acrylamide with
acrylate esters. In embodiments, other suitable the third
components include homopolymers and copolymers of acrylic acid or
methacrylic acid, acrylonitrile or methacrylonitrile, acrylamide or
methacrylamide, vinyl acetate, vinyl pyrrolidone, maleic acid,
maleic anhydride, itaconic acid, itaconic anhydride, vinyl sulfonic
acid or hydroxyalkyl esters of such acids, 0 to 95% by weight of
the acid groups being neutralized with alkali or ammonium groups
and these polymers/copolymers are crosslinked by means of
polyfunctional compounds. Graft copolymers of starch or cellulose
with the above comonomers can also be used in certain embodiments.
Still other suitable superabsorbent polymers include crosslinked
acrylate polymers, crosslinked products of vinyl alcohol-acrylate
copolymers, crosslinked products of polyvinyl alcohols grafted with
maleic anhydride, cross-linked products of acrylate-methacrylate
copolymers, crosslinked saponification products of methyl
acrylate-vinyl acetate copolymers, crosslinked products of starch
acrylate graft copolymers, crosslinked saponification products of
starch acrylonitrile graft copolymers, crosslinked products of
carboxymethyl cellulose polymers, and crosslinked products of
isobutylene-maleic anhydride copolymers.
[0035] In some embodiments, the SA-SHM also includes a tackifying
resin or resins to increase the tackiness of the melt. In
particular embodiments, various colophony derivatives, i.e., in
particular the resin esters of abietic acid, are used for the
tackifying resin; although, in other embodiments, other
polyterpenes and terpene/phenol resins are used. Other colophony
derivatives include colophony esters of various mono- and
poly-functional alcohols. Additionally, suitable tackifying resins
include wood rosin, tall oil rosin, tall oil derivatives, gum
rosin, rosin ester resins, natural terpenes, synthetic terpenes,
and petroleum based tackifying agents, including, e.g., aliphatic,
aromatic and mixed aliphatic-aromatic petroleum based tackifying
resins. Still further, other suitable tackifying resins include,
e.g., alpha-methyl styrene resins, branched and unbranched C.sub.5
resins, C.sub.9 resins and C.sub.10 resins, styrenic and
hydrogenated modifications thereof, and combinations thereof.
[0036] In particular embodiments, the SA-SHM coating contains the
following components: 15 to 45% by weight of resin esters or
terpene/phenol resins; 15 to 40% by weight of thermoplastic
copolymer, more particularly ethylene/vinyl acetate copolymer; 5 to
20% by weight of acrylate copolymers; 5 to 30% by weight of
polyethylene glycols; 5 to 15% by weight of polyvinyl ethyl ethers,
water-soluble or water-dispersible acrylate polymers or
water-soluble or water-dispersible copolyesters; 15 to 50% by
weight of powder-form polyacrylic acid salt, polyacrylamide or
similar powdered superabsorbent polymer; and 0.2 to 2.0% by weight
of stabilizers, such as, for example, antioxidants based on
sterically hindered phenols, that enhance the temperature stability
of the compositions.
[0037] In other particular embodiments, the SA-SHM contains the
following components: 15 to 45% by weight of resin esters,
terpene/phenol resins or the like; 15 to 40% by weight of
thermoplastic polymer or copolymer, more particularly
ethylene/vinyl acetate copolymer; 5 to 25% by weight of
polyethylene glycols; 15 to 50% by weight of a powdered
superabsorbent polymer, more particularly polyacrylic acid salt;
0.2 to 2.0% by weight of a stabilizer; and 0.5 to 5.0% by weight of
waxes, more particularly ethylene bis-stearamide.
[0038] In another embodiment of a suitable SA-SHM coating
composition, the SA-SHM coating is comprised of 10 to 25% by weight
of at least one tackifying resin, 20 to 40% by weight of at least
one water-dispersible EVA wax, 5 to 25% by weight of at least one
ethylene/acrylic acid copolymer, 15 to 35% by weight of at least
one water-soluble homopolymer or copolymer, and 20 to 40% by weight
of at least one powdered superabsorbent polymer having an average
particle size of less than 80 microns.
[0039] The tackifying resins can be selected from the same group of
tackifying resins discussed above. The water-dispersible EVA waxes
are selected from polyethylene waxes based on an ethylene/vinyl
acetate copolymer having a vinyl acetate content of up to 15% and
molecular weights of between 500 and about 10,000. Flexibilizing
ethylene copolymers, particularly ethylene/alkyl acrylate
copolymers having an alkyl acrylate proportion of 15 to 40% by
weight, are suitable as hydrophobic matrix components for binding
the powdered superabsorbent polymer. Longer-chain alkyl acrylic
esters are particularly suitable as comonomers in this respect,
particularly the C.sub.4-C.sub.12 alkyl acrylates.
[0040] The water-soluble homopolymer or copolymer can include
polyethylene glycol, ethylene oxide/propylene oxide copolymers
(either as block copolymers or as random copolymers having a
predominate proportion of ethylene oxide), polyvinyl methyl ether,
polyvinyl pyrrolidone, polyvinyl alcohol, and copolymers of such
monomers with other olefinically unsaturated monomers. In
embodiments, these water-soluble polymers have molecular weights of
between 1000 and 20,000, they may be liquid at room temperature, or
they may be solid and waxy in cases where higher molecular weights
are used. Suitable powdered superabsorbsent polymers include those
listed above.
[0041] In still another embodiment, the SA-SHM is comprised of 1%
to 25% by weight of a block copolymer, 45% to 75% by weight of a
powdered superabsorbent polymer, 15% to 40% by weight of a
plasticizing oil, and optionally 1% to 5% by weight of a
surfactant. Suitable block copolymers include linear and radial
copolymer structures having the formula (A-B)x or A-B-A, where
block A is a polyvinylarene block, block B is a poly(monoalkenyl)
block, and x is an integer of at least 1. Suitable block A
polyvinylarenes include, e.g., polystyrene,
polyalpha-methylstyrene, polyvinyltoluene and combinations thereof.
Suitable B blocks include, e.g., conjugated diene elastomers
including, e.g., polybutadiene and polyisoprene, hydrogenated
elastomers, ethylene/butylene (hydrogenated butadiene) and
ethylene/propylene (hydrogenated isoprene), and combinations and
mixtures thereof. Suitable powdered superabsorbent polymers include
those listed above.
[0042] Suitable plasticizing oils include, e.g., hydrocarbon oils
low in aromatic content, mineral oil. In a particular embodiment,
the plasticizing oils are paraffinic or naphthenic. In some
embodiments, the SA-SHM can also include tackifying agents, such as
those listed above, up to 40% by weight.
[0043] In an embodiment, the SA-SHM coating includes at least one
of sodium or potassium sodium acrylate or acrylamide copolymers,
cross-linked carboxymethylcellulose, ethylene maleic anhydride
copolymers, cross-linked polyethylene oxide, polyvinyl alcohol
copolymers, or starch-grafted copolymers of polyacrylonitrile.
[0044] Referring to each of the above described SA-SHM coating
compositions, in embodiments, the average particle size of the
superabsorbent polymer powders is between 1 micron and 100 microns.
Broadly, in embodiments, the average particle size of the
superabsorbent polymer powder is less than or equal to 80 microns.
In other embodiments, the average particle size of the
superabsorbent polymer powders is less than or equal to 50 microns.
In still other embodiments, the average particle size of the
superabsorbent polymer powders is less than or equal to 38 microns,
and in yet other embodiments, the average particle size of the
superabsorbent polymer powders is less than or equal to 25 microns.
Further, in embodiments, the average particle size of the
superabsorbent polymer powders is greater than 1 micron, and in
other embodiments, the average particle size of the superabsorbent
polymer powders is greater than 10 microns. Additionally, in
embodiments, less than 50% of the superabsorbent polymer powder
particles have a maximum outer dimension .gtoreq.50 microns. In
still other embodiments, less than 10% of the superabsorbent
polymer powder particles have a maximum outer dimension .gtoreq.38
microns, and in yet other embodiments, less than 10% of the
superabsorbent polymer powder particles have a maximum outer
dimension .gtoreq.25 microns. Further, in embodiments, the
superabsorbent polymer powders have particles that are spherical in
shape.
[0045] Additionally, in some embodiments, low-smoke, zero halogen
(LSZH) and/or other fire retardant additives are added to the
SA-SHM. Exemplary fire retardant additives include aluminum
trihydrate, magnesium hydroxide, smoke suppressant molybdenum-based
particles, ammonium polyphosphate, and pentaerythritol.
[0046] As mentioned above, the SA-SHM coating can be applied to the
inner surface 14 of the cable jacket 12, to the exterior or
interior surface of the buffer tubes 22, and/or to the optical
fibers 20. The SA-SHM can be applied to these surfaces via a
variety of application methods. In exemplary embodiments, the
SA-SHM is applied to the jacket 12, buffer tubes 22, and/or optical
fibers 20 by atomizing, fiberizing, dip coating, spray, or by
co-extrusion (e.g., extruding the coating 30 at the same time as
the cable jacket 12, buffer tube 22, and/or jacket for the optical
fiber 20). Thus, the multitude of different application methods
provides low cost and flexible manufacturing. Further, the
components of the optical fiber cables can be coated at different
stages in the manufacturing process, thereby enabling more options
for custom manufacturing. Further, the application of the SA-SHM
coating is not limited with respect to buffer tube or cable length
(i.e., the SA-SHM coating can continuously be applied to the cable
component regardless of the length of that component).
[0047] Indeed, in embodiments, the SA-SHM coating 30 is applied
continuously along the entire length or at least a substantial
portion of the entire length of the cable jacket 12, buffer tube
22, and/or optical fiber 20. However, in another embodiment, the
coating 30 is applied discontinuously. In an exemplary embodiment
shown in FIG. 3A, the coating 30 is applied discontinuously along
the length of an optical fiber 20 (while not depicted, the coating
30 can also be applied discontinuously along the length of the
cable jacket 12 and/or buffer tube 22). As can be seen, the optical
fiber 20 has alternating coated sections 36 and uncoated sections
38 (only one uncoated section 38 is depicted in FIG. 3A). The first
coated section 36 has a length d.sub.1, followed by an uncoated
section 38 having a length d.sub.2, which is followed by another
coated section 36 having a length d.sub.3. In embodiments, the
lengths d.sub.1, d.sub.2, and d.sub.3 are the same length; however,
in other embodiments, the lengths d.sub.1, d.sub.2, and d.sub.3 are
different lengths. Further, in embodiments, the lengths d.sub.1 and
d.sub.3 of the coated sections 36 can be the same length, which is
different than the length d.sub.2 of the uncoated section. In
embodiments, the lengths d.sub.1, d.sub.2, and d.sub.3 are all
between 1 mm and 500 mm in length. In another embodiment, the
lengths d.sub.1, d.sub.2, and d.sub.3 are all between 1 mm and 100
mm in length.
[0048] Additionally, the SA-SHM coating 30 can be applied
discontinuously around the interior circumferential surface of the
cable jacket 12, discontinuously around the exterior or interior
circumferential surface of the buffer tube 22, and/or
discontinuously around the exterior circumferential surface of the
optical fiber 20. FIG. 3B provides an exemplary embodiment of an
optical fiber 20 with a discontinuous coating 30 (while not
depicted, the coating 30 can also be applied discontinuously around
the inner circumference of the cable jacket 12 and/or buffer tube
22). As can be seen in the cross-sectional view of the embodiment
depicted in FIG. 3B, the optical fiber 20 includes a core region 40
along which optical signals travel, a cladding region 42 that keeps
the optical signals substantially within the core region 40, and an
optical fiber jacket 44. In the embodiment depicted, the coating 30
is applied over the optical fiber jacket 44; however, in other
embodiments, the coating 30 can be applied on the exterior surface
of the cladding region 42. As shown in FIG. 3B, the optical fiber
20 has a coated section 36 and an uncoated section 38. In
embodiments, the coated section 36 covers between 5% and 75% of the
circumference of the optical fiber 20. In another embodiment, the
coated section 36 covers between 5% and 50% of the circumference of
the optical fiber 20, and in still another embodiment, the coated
section 36 covers between 5% and 25% of the circumference of the
optical fiber 20.
[0049] In still another embodiment, the coating 30 is discontinuous
along the length and around the circumference of the interior
surface of the cable jacket 12, the exterior or interior surface of
the buffer tube 22, and/or the optical fiber 20.
[0050] Additionally, in another embodiment, the coating 30 is
applied in an optical fiber ribbon cable 50. Referring to FIG. 4,
an optical fiber ribbon cable 50 is shown according to an exemplary
embodiment. Cable 50 is substantially the same as cable 10 (as
shown in FIG. 1) except as discussed herein. As shown in FIG. 4,
cable 50 includes a single buffer tube 52, and a stack 54 of a
plurality of optical fiber ribbons 56. Each optical fiber ribbon 56
includes a plurality of optical fibers 20 surrounded by and
supported by a polymeric matrix 58. In various embodiments, cable
50 includes at least four ribbons within stack 54 and each ribbon
56 supports four optical fibers 20. Similar to the previous
embodiments, the SA-SHM coating 30 is applied to at least one of
the following locations within the cable 50: at least partially
along the length of at least one of the optical fiber ribbons 56 in
the buffer tube 52, at least partially along the length of the
exterior or interior surface of the buffer tube 52, or at least
partially along the length of the interior surface of the cable
jacket 12. Additionally, in embodiments similar to those previously
described, the SA-SHM coating 30 is applied discontinuously along
the length of the ribbon 56 and/or discontinuously along the length
and/or around the circumference of the inner surface of the cable
jacket 12 and/or buffer tube 52.
[0051] Tables 1-3, below, provide examples of the water absorption
capabilities of four SA-SHM (referred to individually as "SHM1,"
"SHM2," "SHM3," and "SHM4") that can be used as the coatings
according to exemplary embodiments. Certain SA-SHM capabilities are
compared against a standard SAP powder (referred to as "SAP1"). In
particular, SHM1 is commercially available as NW1117 from H.B.
Fuller Company, Vadnais Heights, Minn. SHM2 is commercially
available as NW1120B from H.B. Fuller Company, Vadnais Heights,
Minn. SHM3 is commercially available as HM002 from Stewart
Superabsorbents, Hickory, N.C. SHM4 is commercially available as
HM008 from Stewart Superabsorbents, Hickory, N.C. SAP1 is a
powderized sodium acrylate polymer having particles with average
size of about 63 microns (commercially available from Stewart
Superabsorbents, Hickory, N.C.). All experiments were performed at
room temperature of about 22.degree. C.
[0052] The data displayed in Table 1 demonstrates the water
absorption capacities of SHM1 and SHM2 as compared to SAP1. In
particular, particles of SAP1 and sections of SHM1 and SHM2 were
placed in a beaker. The masses of each beaker before and after the
addition of SAP1, SHM1, and SHM2 were determined so as to calculate
the amount of each material added. A filter as then placed over the
beaker, and the mass of the beaker/material/filter combination was
determined. Water was added to the beaker, and the materials were
given time to absorb as much water as they could. Any remaining,
unabsorbed water was drained from the beaker, and the mass of the
beaker/material/filter/absorbed water was determined. As can be
seen from Table 1, SHM1 and SHM2 absorbed more water on a per gram
basis than SAP1.
TABLE-US-00001 TABLE 1 Water absorption capacity of SHM Materials
compared to SAP Powder Material SAP1 SHM2 SHM1 Mass of Beaker +
Stir Bar (g) 129.70 70.10 136.15 Mass of Beaker + Stir Bar + SHM
129.84 70.23 136.32 Material (g) Mass of SHM Material (g) 0.14 0.13
0.17 Mass of Beaker + Filter Assembly (g) 156.80 157.05 150.62 Mass
of Beaker + Filter Assembly + 181.64 179.24 180.56 Swollen Gel (g)
Mass of Water Absorbed (g) 24.69 22.05 29.76 Mass of Water
Absorbed/Mass of SHM 165.69 167.81 175.06 Material (g/g)
[0053] The data displayed in Table 2 demonstrates the water
absorption capacities of SHM3 and SHM4 as compared to SAP1. In this
experiment, the materials were placed on a glass slide. Each of the
glass slides were weighed before and after the materials were
placed thereon to determine the mass of each material deposited.
Water was then added dropwise on the materials over a time up to 10
minutes and until it was visually observed that the material was
saturated and the extra water dripped off. The glass slides with
gelled material were then weighed to determine the amount of water
absorbed. As can be seen in Table 2, SHM3 and SHM4 performed as
well or better than SAP1 in terms of water absorbed on a per gram
basis.
TABLE-US-00002 TABLE 2 Water absorption capacity of SHM materials
in experiments of films on glass slide Material SHM3 SHM4 SAP1 Mass
of Glass Slide (g) 9.272 9.263 9.263 Mass of Glass Slide + Material
(g) 9.347 9.348 9.348 Mass of Glass Slide + Gelled Material (g)
19.468 19.650 19.650 Mass of Material (g) 0.075 0.085 0.082 Mass of
Water Absorbed (g) 10.121 10.302 10.305 Mass of Water Absorbed/Mass
of Gelled 135.66 121.06 125.67 Material (g/g)
[0054] The results of a third experiment are provided in Table 3.
In this experiment, SHM3 was coated onto an optical fiber. The
optical fiber was taped to a glass slide, and SHM3 was applied over
the optical fiber. The mass of the optical fiber and glass slide
was determined before and after SHM3 was applied. Water was then
introduced to the coated optical fiber, and the mass of the water
absorbed was determined. As can be seen in Table 3, SHM3 performed
as well when coating the optical fiber as when it was by itself on
the glass slide.
TABLE-US-00003 TABLE 3 Water absorption capacity of SHM material
film on an optical fiber SHM Material SHM3 Mass of Glass Slide (g)
9.2518 Mass of Glass Slide + Taped Fiber (g) 9.2905 Mass of Glass
Slide + Taped Fiber + SHM (g) 9.3075 Mass of Glass Slide + Taped
Fiber + SHM + Water (g) 11.6125 Mass of SHM Material (g) 0.017 Mass
of Water Absorbed (g) 2.305 Mass of Water Absorbed/Mass of SHM
Material (g/g) 135.59
[0055] FIG. 5 provides a graph of the water swelling capacity of
SHM1, SHM2, and SHM3. In this instance, the water swelling capacity
was measured in terms of the increase in thickness as compared to
the original thickness of the SA-SHM film. As can be seen from the
graph of FIG. 5, SHM1, SHM2, and SHM3 each increased in thickness
by more than 100 times their original thicknesses. Further, SHM1
and SHM3 exhibited a faster absorption rate than SHM2. Generally, a
faster absorption rate is more advantageous for optical fiber cable
applications.
[0056] Advantageously, embodiments of the optical fiber cable using
the SA-SHM coating on at least one surface or component therein
provide the benefit of reducing microbending losses (and thereby
optical fiber attenuation) as compared to SAP powders, especially
in small size optical fiber cable designs. Further, the reduction
in microbending can allow for lower cost, more compact cable
designs. Moreover, using the SA-SHM coating prevents sticking of
the optical fibers to the buffer tubes and/or of the buffer tubes
to the jacket in contrast to some optical fiber cables that use of
SAP gels as a means of water absorption. Additionally, lower cost
water-blocking functionality can be provided through the enhanced
control of the quantity of SA-SHM used through the length of the
cable as compared to SAP coated polyester tapes and yarns and SAP
powders. In accordance with yet other aspects of the present
disclosure, the SA-SHM can be selectively applied to, for example,
the interstices spaces in a cable such that attenuation losses may
be further reduced.
[0057] Indeed, optical fiber cables having a small form factor,
such as those provided by embodiments of the SA-SHM coated optical
fiber cables disclosed herein, allow higher fiber density cable
installations and help overcome duct congestion issues.
Additionally, the cost of such optical fiber cables tends to be
lower because of the lower material cost and because they
facilitate larger installed lengths during blowing of cables in
ducts/micro-ducts.
[0058] Unless otherwise expressly stated, it is in no way intended
that any method set forth herein be construed as requiring that its
steps be performed in a specific order. Accordingly, where a method
claim does not actually recite an order to be followed by its steps
or it is not otherwise specifically stated in the claims or
descriptions that the steps are to be limited to a specific order,
it is in no way intended that any particular order be inferred. In
addition, as used herein, the article "a" is intended to include
one or more than one component or element, and is not intended to
be construed as meaning only one.
[0059] It will be apparent to those skilled in the art that various
modifications and variations can be made without departing from the
spirit or scope of the disclosed embodiments. Since modifications,
combinations, sub-combinations and variations of the disclosed
embodiments incorporating the spirit and substance of the
embodiments may occur to persons skilled in the art, the disclosed
embodiments should be construed to include everything within the
scope of the appended claims and their equivalents.
* * * * *